This was a retrospective, cross-sectional, single-center study conducted after approval by the ethical review committee. The radiology database of Aga Khan University Hospital, Karachi, Pakistan was searched for patients who had keywords “appendiceal mucocele” in CT reports from January 2009-2019. Only cases with histopathologic examination of the lesions obtained after surgical excision were included. Patients without biopsy results and pediatric patients were excluded from the study.
We used either enhanced or unenhanced CT imaging. The patients who underwent contrast-enhanced CT received 1.5 mL/kg iohexol (300 mg I/mL, Omnipaque, GE Healthcare) through an 18-gauge angiographic catheter inserted into a forearm vein. A mechanical injector was used to administer that agent at a rate of 2.5–3 mL/s. Enhanced CT was performed with an 80- to 90-second delay after IV injection.
Preoperative CT studies in patients were analyzed retrospectively and in consensus by two body-imaging radiologists. The readers were unaware of the radiologic and pathologic diagnoses but were informed that the subjects included patients who had inflammatory mucoceles, benign mucoceles,or malignant cystadenocarcinoma. Short axis diameter, shape of cystic dilatation (round, tubular, or other), wall contour (smooth or irregular), attenuation of intraluminal contents, and maximal wall thickness were assessed. The presence of mural calcifications, internal septations, soft-tissue thickening, periappendiceal fat stranding, presence of appendicolith, intraperitoneal free fluid, wall enhancement (in contrast-enhanced scans) and presence of pseudomyxoma peritonei were also evaluated. The focal part of the mucocele most significantly distended: base, mid and distal or whether there was generalized dilatation was recorded. According to the pathologic results, patients were classified into three groups: those with inflammatory mucoceles (with coexisting acute appendicitis) (n=10), benign mucocele (simple mucocele and mucosal hyperplasia and low-grade mucinous cystadenoma (n =17), and those with malignant mucinous cystadenocarcinoma (n =4).
In this study, soft-tissue thickening was defined as internal soft-tissue attenuation nodularity of mucoceles. “Irregular wall” was used to describe the contour of mucoceles as opposed to smooth. Pseudomyxoma peritonei was defined as a scalloping effect on the solid organs or septations in ascites.
For each of the binary assessments, Fisher's exact test was used to compare each patient groups in terms of percentage of times a given reader reported a positive finding. Exact p values from a Mann-Whitney U test was used to assess the difference between pairs of patient groups in terms of each numeric and ordinal measure.
Receiver operating characteristics analysis was performed to assess the diagnostic utility of maximal appendiceal luminal diameter in differentiating inflammatory, benign and malignant mucoceles. All reported p values were two-sided without correction for multiple comparisons, and p < 0.05 was declared significant. SPSS software (version 13) was used for all statistical computations.